1. Field of the Invention
This invention relates generally to systems and arrangements for determining the presence of a plurality of environmental conditions in relation to a vehicle, and more particularly, to a system that can control the operation of a device, such as the windows, the convertible roof, the air conditioner, a dehumidifier, the ventilation system, or the windshield wipers of a vehicle, in response to the presence of droplets of liquid on a transparent surface thereof, such as the windshield of the vehicle, the presence of condensation on the interior of the windshield of the vehicle, or the presence of smoke in the vehicle.
2. Description of the Related Art
Numerous efforts have been made in the prior art to provide a system that reliably will control the windshield wipers of a vehicle in response to the presence of water on the windshield. In addition to falling to meet the level of reliability required to avoid the annoying and distracting false triggering of windshield wipers, the majority of the known arrangements must be installed directly onto the windshield, resulting in unsightly wiring extending from a sensor that has been bonded to the interior of the windshield. With respect to the false triggering of the windshield wipers, many of the known arrangements will trigger a false indication of rain in response to fluctuations in the ambient light, as would be the case with a vehicle traveling under the shadows of telephone poles, or under highway lamps.
Existing optical rain sensors of the type that are usually installed within vehicles are mounted on the windshield in the wiper path. Optical sensors generally include a light source, such as an LED, and a photodetector, usually a phototransistor or a photodiode, arranged such that when no raindrops are on the windshield, light from the LED is totally internally reflected at the outside surface of the windshield to a photodiode. If a drop of rain is deposited on the windshield where the light beam is reflected, the conditions for total internal reflection are violated, and the intensity of light in the reflected beam is reduced. In these known systems, a relatively large array of LEDs and photodiodes are required to monitor a few square inches on the windshield. The extent of the monitored region of the windshield must be sufficiently large to provide an accurate sample of the random distribution of raindrops that fall on the surface of the windshield. As stated, the array of LEDs and photodiodes must be mounted inside the vehicle on the windshield in the wiper path.
Another problem associated with known arrangements is that of cost. In most of the presently available designs, one photodetector is required for each LED in the array. There is, therefore, a need for a rain sensor that is economical and which need not be installed on the windshield of the vehicle.
In addition to water depositing on the outer surface of the windshield, water will collect on the interior of the windshield in the form of condensed water vapor, sometimes called "fog." Such condensed water vapor can, within a matter of minutes, reduce the visibility through the window to a dangerous level. In such situations, it is essential that the defogger function be carried out by cycling the air conditioner to dehumidify the air. The operation of the air conditioner generally will decrease the amount of fog on the interior of the windshield in a relatively short period of time.
It is additionally useful in a vehicle to reduce the accumulation of smoke in the cabin of the vehicle which would result from the smoking of tobacco by the occupants. On occasion, the operator of the vehicle would be reluctant to embarrass a smoking passenger by obvious manipulation of the ventilator controls. Accordingly, it would be desirable for the ventilator to be operated automatically in response to the presence of smoke in the cabin.
A significant further problem with known arrangements that employ commercially available light-emitting devices is that as the devices age, or as they are subjected to increased temperature, their light output diminishes. Thus, over time, the amplitude of the light output will drift, causing false readings. There is a need, therefore, for an arrangement that will reliably detect the presence of water droplets on a vehicle windshield, as well as other environmental conditions, while maintaining immunity from the effects of age and temperature.
It is, therefore, an object of this invention to provide an arrangement that is simple and will reliably detect the presence of water droplets on the outside of a windshield of a vehicle.
It is another object of this invention to provide an arrangement that is simple and will reliably detect the presence of condensed water vapor on the inside of a windshield of a vehicle.
It is also an object of this invention to provide an arrangement that is simple and will reliably detect the presence of smoke in the cabin of a vehicle.
It is a further object of this invention to provide a system for automatically operating the windshield wipers of a vehicle in response to the presence of water on the windshield.
It is additionally an object of this invention to provide a system for automatically operating an air conditioning or dehumidification system of a vehicle in response to the presence of condensed water vapor on the windshield.
It is yet a further object of this invention to provide a system for automatically operating the cabin ventilation system of a vehicle in response to the presence of smoke, such as cigarette smoke, in the cabin of the vehicle.
It is also another object of this invention to provide a system that responds to the effect on light by several environmental conditions, while maintaining immunity to variations in the ambient light levels.
It is yet an additional object of this invention to provide a system that responds to the effect on light by several environmental conditions, while maintaining immunity to the effects of age and temperature on light-emitting components.
It is still another object of this invention to provide a system that responds redundantly to the effect on light by several environmental conditions to ensure reliable operation and reduce false operations.
It is a yet further object of this invention to provide a windshield wiper control sensor that need not be installed directly on the windshield of the vehicle.
A still further object of this invention is to provide a system that responds to the effect on light by several environmental conditions, in the vicinity of the windshield of the vehicle, without the need for establishing a direct contact between the system and the windshield.
An additional object of this invention is to provide a windshield wiper control sensor that can be installed on the instrument panel of the vehicle.